evolutionary explanations

• natural selection

  selection of characteristics that provide an offspring survival advantage
• sexual selection

  selection of characteristics that provide an immediate reproductive advantage
• two forms of sexual selection

  1. inter-sexual selection
  2. intra-sexual selection
• inter-sexual selection

  • strategies one sex uses to attract others
  • members of one sex evolve with preferences for desirable qualities in the other sex
  • members posssessing these qualities are more likely to make and pass their genes
  • preferred by females
  • are more choose as they have more to lose, so look for more of these qualities (quality over quantity)
• because females are more choosy, inter-sexual selection effects are more often seen in males of species. this leads too...

  runaway process and sexy sons

  • fisher (1930) proposed a process wereby adaptive features will be selected by females when choosing a mate
  • over several generations, these features become exaggerated (a 'runaway process).
  • this is known as the 'sexy sons' hypothesis
• 'sexy sons' hypothesis

  • suggests females choose a sexual partner for successful and attractive attributes
  • likely passed on to future generations
  • therefore, her sons are likely to possess desirable characteristics from both parent making it even more likely for them to mate in the future
• intra-sexual selection

  • members of the same sex compete with one another to gain access to members of the opposite sex
  • the successful individual is able to make and pass on genes
  • leads to 'dimorphism' i.e. accentuation of secondary sexual characteristics in those with greater reproductive fitness e.g. height
  • preferred by males
  • anisogamy = men's optimum strategy is to outcompete peers and to mate with as many females as possible as it is low energy to produce sperm
• evaluation - buss (1989) - procedure

  explored what we look for in a long-term partner

  procedure:

  • study had 10,000 people from 37 different cultures
  • asked to rate each of 18 characteristics on how important they would be in choosing a mate
  • four-point scale was used, ranging from '3' (indispensable) to '0' (irrelevant)
• buss - findings

  • resources: more women desired 'good financial prospects' - men with resources, or qualities like ambition
  • physical attractiveness: men placed more importance on this - provides cues to woman's health - her fertility + reproductive value
  • youth: men universally want younger mates - valued increased fertility
  • other important characteristics: both sexes want intelligence (linked to parenting skill) and kind (linked to interest in long-term relationships
• • buss is supporting research for inter and intra sexual selection.
  • is a questionnaire = replicable, cover a large sample quickly
  • however answers are limited/subjective, demand characteristics may interfere, there is a social desirability bias
• criticism of buss

  • self-report methodology may have validity issues
  • his questionnaire only indicates expressed preferences
  • psychologists argue measures of real-life behaviour (eg, marriage statistics) would be more valid
  • suggests caution must be taken when researching evolutionary explanations
  • buss' findings may lack temporal validity (findings may change over years)
• criticism of buss (2)

  hard to separate evolved preferences from cultural traditions

  • kasser + sharma (1999) = analysed 37 different cultures = found women value resources more in cultures where status and education opportunities limited
  • suggests partner preferences are not universal - social + economic factors in mate preferences shouldnt be underestimated
• further supporting of research on sexual selection

  • penton-voak et al (1999) found female mate choice varies during menstrual cycle
  • prefer a slightly feminised male face when looking for a long-term partner
  • HOWEVER during ovulation, women prefer a more masculine face
  • suggest intersexual selection may favour females who pursue mixed mating strategies
• supporting evidence for intersexual selection + 'ornamental' traits in males

  • nettle + clegg (2006) studied the sexual 'prowess' of creative and non-creative partners
  • found the creatives had more sexual partners than control group of non-creatives
  • suggests certain traits evolve for reproductive reasons alone, even with no survival benefits
• • women wouldn't choose creatives because they won't have stable resources to provide them with
  • however sexual overpowers natural because of physical characteristics, with women knowing they may not provide for them
• criticism of evolutionary explanations

  • cannot be generalised to all types of relationships
  • only apply to relationships where there is a desire to procreate
  • this theory is also deterministic and reductionist
• criticisms of evolutionary explanations (2)

  • gobrogge et al. (2007) did a content analysis of personal advertisements of the internet
  • sexual encouters were sought more by homosexual than heterosexual men = suggesting partner preferences are independent of evolutionary drives to procreate
  • addition, heterosexual men prefer a wider age range for short-term relation than ones seeking long-term
• why do gobrogge et al's finding criticise evolutionary theories of partner preferences?

  • it cannot explain homosexual relationships
  • goes against evolutionary preferences of only men wanting to bear a child